1. Field of the Invention
The present invention relates to a method of detecting the connection of a battery pack to a portable or mobile electronic device such as mobile phones and a mobile electronic device using the method. More particularly, the invention relates to a method of detecting whether or not a specific battery pack is connected to the body of a mobile electronic device that makes it possible to recognize the connection and type of the battery pack without providing discrimination-dedicated terminals, and a mobile electronic device capable of connection of battery packs having different characteristics.
2. Description of the Related Art
In recent years, various portable or mobile electronic equipment such as mobile or cellular phones, personal handyphone systems (PHSs), notebook computers, and digital cameras, have been developed and extensively used. The mobile electronic equipment, which may be termed xe2x80x9cmobile electronic devicesxe2x80x9d later, require high-level transportability and therefore, they need to be compact and light-weight and operable with a battery pack as its power supply.
Typically, the battery pack applicable to portable electronic equipment comprises at least one chargeable battery cell in its inside. Several types of chargeable battery cells have been already developed and commercially produced and sold for this purpose. They are different in battery characteristics such as capacity, discharge characteristic, and necessary charging period from each other. According to the types of chargeable battery cells, several types of battery packs have been already commercially produced and sold so far.
To make it possible to apply different types of battery packs to mobile electronic devices of this sort, mobile electronic devices need to discriminate the type of sort of battery packs connected or installed and to switch their operating condition according to the current type/sort of battery packs. Also, with mobile electronic devices chargeable without separating battery packs, the charging voltage to battery packs is required to be controlled or adjusted in the devices according to the current type/sort of battery packs.
To meet the above-described requirement, conventionally, prior-art mobile electronic devices capable of using different types of battery packs comprises dedicated terminals for discriminating the type of battery packs connected. The discrimination-dedicated terminals are provided in both battery packs and the body of devices.
As an example of mobile electronic devices of this sort, a conventional mobile phase capable of the alternative use of two different types of battery packs is explained below with reference to FIGS. 1 to 3.
FIGS. 1 and 2 are schematic, partial circuit diagrams of two different-type battery packs for a conventional mobile phone, respectively. FIG. 3 is a schematic, partial circuit diagram of the body of the same phone.
As shown in FIG. 1, a first battery pack 40 comprises a switch (SW) 41, a protection circuit 42, a lithium (Li)-ion battery cell 43, a thermistor 44, a resistor 45, a power supply terminal (i.e., +V terminal) 401, a discrimination terminal (i.e., SEL terminal) 402, a temperature detection terminal (i.e., TH terminal) 403, and a ground terminal (i.e., GND terminal) 404. The switch 41, the protection circuit 42, the cell 43, the thermistor 44, and the resistor 45 are provided in the enclosure or casing (not shown) of the first battery pack 40. The power-supply terminal 401, the discrimination terminal 402, the temperature detection terminal 403, and the ground terminal 404 are exposed to the outside from the enclosure.
The positive terminal of the battery cell 43 is connected to the power-supply terminal 401 by way of the switch 41. The negative terminal of the battery cell 43 is directly connected to the ground terminal 401. The battery voltage VBAT1, which is generated between the positive and negative terminals of the cell 43, is outputted from the power supply and ground terminals 401 and 404.
The protection circuit 42 is supplied with the battery voltage VBAT1 from the cell 43. The circuit 42 generates the switch control signal VSW1 on the basis of the voltage VBAT1 and then, supplies the signal VSW1 thus generated to the switch 41. The ground terminal of the circuit 42 is connected to the ground terminal 404.
The switch 41 serves to connect the positive terminal of the battery cell 43 to the power supply terminal 401 or disconnects the same from the terminal 401 according to the switch control signal VS1 from the protection circuit 42.
The resistor 45 is connected across the discrimination terminal 402 and the ground terminal 404.
The thermistor 44 is connected across the temperature detection terminal 403 and the ground terminal 404. To facilitate detection of the temperature of the cell 43, the thermistor 44 is located in the vicinity of the battery cell 43 in the battery enclosure.
With the first battery pack 40 having the above-described configuration, the switch 41 is turned on or off by the control signal VSW1 from the protection circuit 42, thereby controlling the output of the battery voltage VBAT1 from the power-supply and ground terminals 401 and 404. Specifically, in the normal operation state where the voltage VBAT1 is equal to or higher than a specific value, the switch 41 is turned on by the control signal VSW1, outputting the voltage VBAT1 from the terminals 401 and 404. On the other hand, in the abnormal operation state where the voltage VBAT1 is less than the specific value, the switch 41 is turned off by the control signal VSW1, stopping the output of the voltage VBAT1 from the terminals 401 and 404.
The resistance RTH1 of the thermistor 44 varies according to the temperature of the battery cell 43. Thus, when a proper circuit that generates a voltage corresponding to the resistance RTH1 is connected to the temperature detection terminal 403, the temperature of the cell 43 can be detected on the basis of the voltage thus generated.
When a specific circuit is connected to the discrimination terminal 403, the type or sort of the first battery pack 40 can be discriminated.
Next, a second battery pack 50 is explained below.
As shown in FIG. 2, the second battery pack 50 has approximately the same configuration as the first battery pack 40 except that a resistor 55 corresponding to the resistor 45 is connected across a power supply terminal 501 and a discrimination terminal 502.
Specifically, the second battery pack 50 comprises a switch 51, a protection circuit 52, a Li-ion battery cell 53, a thermistor 54, a resistor 55, a power-supply terminal 501, a discrimination terminal 502, a temperature detection terminal 503, and a ground terminal 504. The switch 51, the protection circuit 52, the cell 53, the thermistor 54, and the resistor 55 are provided in the enclosure (not shown) of the pack 50. The power-supply terminal 501, the discrimination terminal 502, the temperature detection terminal 503, and the ground terminal 504 are exposed to the outside from the enclosure. The battery cell 53 is different in characteristic from the battery cell 43.
The positive terminal of the cell 53 is connected to the power-supply terminal 501 by way of the switch 51. The negative terminal of the cell 53 is directly connected to the ground terminal 504. The battery voltage VBAT2, which is generated between the positive and negative terminals of the cell 53, is outputted from the power-supply and ground terminals 501 and 504.
The protection circuit 52 is supplied with the battery voltage VBAT2 from the cell 53. The circuit 52 generates the switch control signal VSW2 on the basis of the voltage BBAT2 and then, supplies the signal VSW2 thus generated to the switch 51. The ground terminal of the circuit 52 is connected to the ground terminal 504.
The switch 51 serves to connect the positive terminal of the battery cell 53 to the power supply terminal 501 or disconnects the same from the terminal 501 according to the switch control signal VSW2 from the protection circuit 52.
The resistor 55 is connected across the discrimination terminal 502 and the ground terminal 504.
The thermistor 54 is connected across the temperature detection terminal 503 and the ground terminal 504. To facilitate detection of the temperature of the cell 53, the thermistor 54 is located in the vicinity of the battery cell 53 in the battery enclosure.
With the second battery pack 50 having the above-described configuration, similar to the first battery pack 40 shown in FIG. 1, the switch 51 is turned on or off by the control signal VSW2 generated by the protection circuit 52, thereby controlling the output of the battery voltage VBAT2 from the power-supply and ground terminals 501 and 504. Specifically, in the normal operation state where the voltage VBAT2 is equal to or higher than a specific value, the switch 51 is turned on by the control signal VCON2, outputting the voltage VBAT2 through the terminals 501 and 504. On the other hand, in the abnormal operation state where the voltage VBAT2 is less than the specific value, the switch 51 is turned off by the signal VSW2, stopping the output of the voltage VBAT2 through the terminals 501 and 504.
The resistance RTH2 of the thermistor 54 varies according to the temperature of the battery cell 53. Thus, the similar to the first battery pack 40, when a proper circuit that generates a voltage corresponding to the resistance RSW2 is connected to the temperature detection terminal 503, the temperature of the cell 53 can be detected on the basis of the voltage thus generated.
When a specific circuit is connected to the discrimination terminal 503, the type or sort of the second battery pack 50 can be discriminated.
Subsequently, the body of the mobile phone, i.e., the phone body 60, is explained below with reference to FIG. 3.
As shown in FIG. 3, the phone body 60 comprises a switch 61, a charging controller 62, two comparators 63 and 64, a diode 65 for stopping the reverse current, four resistors 66, 67, 68, and 69, a power supply IC (Integrated Circuit) 70 with specific control functions, a power supply terminal 60, a discrimination terminal 602, a temperature detection terminal 603, two ground terminals 604 and 606, and a charging terminal 605. The switch 61, the charge control section 62, two comparators 63 and 64, the diode 65, the resistors 66, 67, 68, and 69, and the power supply IC 70 are provided in the enclosures (not shown) of the body 60. The power supply terminal 601, the discrimination terminal 602, the temperature detection terminal 603, the ground terminals 604 and 606, and the charging terminal 605 are exposed to the outside from the enclosure. The ground terminal 604 is used for connection of the first or second battery pack 40 or 50. The ground terminal 606 is used for connection of a specific charging device.
The power supply terminal 601 is connected to the ground terminals 604 and 606 by way of the serially-connected resistors 66 and 67. Also, the terminal 602 is connected to the charge input terminal 605 by way of the switch 61 and the diode 65. The terminal 601 is further connected to the power supply IC 70 incorporated into the inside of the body 60.
The serially-connected resistors 68 and 69 are connected parallel to the serially-connected resistors 66 and 67 between the power supply terminal 601 and the ground terminal 604.
The discrimination terminal 602 is connected to the connection point of the resistors 68 and 69 and the input terminal of the first comparator 63. The resistors 68 and 69 serve as a pull-up resistor and a pull-down resistor for the terminal 602, respectively. The output terminal of the first comparator 63 is connected to the charging controller 62 and thus, the output signal VCOMP1 of the first comparator 63 is inputted in to the controller 62.
The temperature detection terminal 603 is connected to the connection point of the resistors 66 and 67 and the input terminal of the second comparator 64. The resistors 66 and 67 serve as a pull-up resistor and a pull-down resistor for the terminal 603, respectively. The output terminal of the second comparator 64 to connected to the charging controller 62 and thus, the output signal VCOMP2 of the second comparator 64 is inputted in to the controller 62.
The charging controller 62, which is connected to the cathode of the diode 65 and the ground terminal 606, receives the output signals VCOM1 and VCOM2 from the first and second comparators 63 and 64. The charging controller 62 controls or adjusts the charge voltage VCHG at the connection point of the switch 61 and the diode 65 on the basis of the output signal VCOM1 of the first comparator 63 thus received. The charging controller 62 outputs the control signal VCW3 to the switch 61 on the basis of the output signal VCOM2 of the second comparator 64 thus received.
The switch 61 serves to connect the diode 65 to the power supply terminal 601 or disconnect if from the terminal 601 according to the control signal VSW sent from the controller 62.
One of the first and second battery packs 10 and 50 is alternately connected to the phase body 60, constituting the mobile phone. This phone to which the first or second battery pack 40 or 50 is connected operates in the following way.
FIG. 4 shows the configuration of the conventional mobile phone having the first battery pack 40, in which the power supply terminal 401, the discrimination terminal 402, the temperature detection terminal 403, and the ground terminal 404 of the first battery pack 40 are connected to the power supply terminal 601, the discrimination terminal 602, the temperature detection terminal 603, and the ground terminal 604 of the phone body 60, respectively.
When the phone body 60 is in its normal operation, the power supply terminal 601 is supplied with the first battery voltage VBAT1 of the first battery pack 40. The first battery voltage VBAT1 thus supplied is then supplied to the power supply IC 70, generating specific inner-circuit voltages with specific values. These inner-circuit voltages are respectively supplied to the inner circuit blocks of the phone body 60, such as the ratio, display, and control sections (not shown).
The first battery voltage VBAT1 supplied by the first pack 40 is divided by the resistor 45 of the pack 40 and the resistors 68 and 69 of the body 60, generating a first discrimination voltage VA at the connection point of the resistor 68 and 69. The first discrimination voltage VA, which has a relatively lower value, is inputted into the first comparator 63. The first comparator 63 generates the output signal VCOM1 having a logic value corresponding to the value of the discrimination voltage VA thus inputted and then, sends the output signal VCOM1 to the charging controller 62 of the phone body 60. According to the output signal VCOM1 thus sent, the controller 62 recognizes that the first battery pack 40 is connected to the body 60.
On the other hand, when the phone body 60 is in its charging operation, a specific charging apparatus (not shown) is connected across the charging terminal 605 and the ground terminal 606, supplying a charge current ICHG to the body 60 through the terminal 605. Part of the charge current ICHG is sent to the charging controller 62 as a control current ICOS, thereby generating the charge voltage VCHG at the connection point of the switch 61 and the diode 65 in the body 60. As explained above, the controller 62 is recognized that the first battery pack 40 has been connected to the body 60 and therefore, the controller 62 controls the value of the control current ICON to thereby adjust the value of the charge voltage VCHG according to the charge characteristic of the battery cell 43.
The charge voltage VCHG thus generated is outputted through the power supply terminal 601 by way of the switch 61 and then, is supplied to the battery cell 43 of the first battery pack 40 by way of the power supply terminal 401 and the switch 41. As a result, a specific charging current is supplied to the cell 43 to charge the same.
The diode 65 of the body 60 serves to prevent the reverse current from flowing toward the charge apparatus from the cell 43.
During the charging operation, the charging voltage VCHG is divided by the thermistor 44 of the pack 40 and the resistors 66 and 67 of the body 60, thereby generating the temperature detection voltage VB that varies dependent on the resistance value RTH1 of the thermistor 44 at the connection point of the resistors 66 and 67. The detection voltage VB thus generated is then inputted into the second comparator 64 of the body 60. The second comparator 64 generates the output signal VCOM2 having a logic value corresponding to the detection voltage VB thus inputted and then, sends the signal VCOM2 to the charging controller 62. Thus, the controller 62 controls the turn on and off operation of the switch 61 according to the signal VCOM2 from the second comparator 64.
When the cell 43 of the first battery pack 40 is excessively charged, the temperature of the cell 43 rises and the resistance RTH1 of the thermistor 44 decreases. Thus, the temperature detection voltage VD at the connection point of the resistors 66 and 67 lowers. The second comparator 64 compares the value of the detection voltage VD with the predetermined threshold value and then, outputs the output signal VCOM2 having a specific logic value if the value of the detection voltage VD is equal to or less than its threshold value. As a result, the charging controller 62 turns the switch 61 off to stop the charging operation toward the first battery pack 40.
Next, the operation of the conventional mobile phone having the second battery pack 50 is explained with reference to FIG. 5.
FIG. 5 shows the configuration of the conventional mobile phone with the second battery pack 50, in which the power supply terminal 501, the discrimination terminal 502, the temperature detection terminal 503, and the ground terminal 504 of the second battery pack 50 are connected to the power supply terminal 601, the discrimination terminal 602, the temperature detection terminal 603, and the ground terminal 604 of the phone body 60, respectively.
When the phone body 60 is in its normal operation, the power supply terminal 601 is supplied with the second battery voltage VBAT2 of the second battery pack 50. The second battery voltage VBAT2 thus supplied is then supplied to the power supply IC 70, generating the specific inner-circuit voltages will specific values. These inner-circuit voltages are respectively sent to the inner circuit blocks or the phone body 60, such as the radio section, the display section, and the control section. This is the same as that of the first battery pack 40.
The second battery voltage VBAT2 supplied by the second pack 50 is divided by the resistor 55 of the pack 50 and the resistors 68 and 69 of the body 60, generating a second discrimination voltage VAxe2x80x2 at the connection point of the resistors 68 and 69. The second discrimination voltage VAxe2x80x2, which has a higher value than the first discrimination voltage VA, is inputted into the first comparator 63. The first comparator 63 generates the output signal VCOM1 having a logic value corresponding to the value of the discrimination voltage VAxe2x80x2 thus inputted and then, sends the output signal VCOM1 to the charging controller 62 of the phone body 60. According to the output signal VCOM1 thus sent, the controller 62 recognizes that the second battery pack 50 is connected to the body 60.
The charging operation is approximately the same as that using the first battery pack 40. Specifically, when the phone body 60 is in its charging operation, a specific charging apparatus (not shown) is connected across the charge input terminal 605 and the ground terminal 606. Thus, a charge current ICHG is supplied to the body 60 through the terminal 605. Part of the current ICHG is sent to the charge controller 62 as the control current ICON, thereby generating the charge voltage VCHG at the connection point of the switch 61 and the diode 65 in the body 60. As explained above, the controller 62 is recognized that second battery pack 50 has been connected to the body 60 and therefore, the controller 62 controls the value of the control current ICON to thereby adjust the value of the charge voltage VCHG according to the charge characteristic of the battery cell 53.
The charge voltage VCHG thus generated is outputted through the power supply terminal 601 by way of the switch 61 and then, is supplied to the battery cell 53 of the second pack 50 by way of the power supply terminal 501 and the switch 51. As a result, a specific current flows to the cell 53 to charge the same.
The diode 65 of the body 60 serves to prevent the reverse current from flowing toward the charge apparatus from the cell 53.
During the charging operation, the charging voltage VCHG is divided by the thermistor 54 of the pack 50 and the resistors 66 and 67 of the body 60, thereby generating the temperature detection voltage VBxe2x80x2 that varies dependent on the resistance value RTH2 of the thermistor 54 at the connection point of the resistors 66 and 67. The detection voltage VBxe2x80x2 thus generated is inputted into the second comparator 64 of the body 60. The second comparator 64 generates the output signal VCOM2 having a logic value corresponding to the voltage VBxe2x80x2 thus inputted and then, sends the signal VCOM2 to the charging controller 62. Thus, the controller 62 controls the turn on and off operation of the switch 61 according to the signal VCOM2 from the second comparator 64.
When the cell 53 of the second battery pack 50 is excessively charged, the temperature of the cell 53 rises and the resistance of the thermistor 54 decreases. Thus, the temperature detection voltage VBxe2x80x2 at the connection point of the resistors 66 and 67 decreases. The second comparator 61 compares the value of the detection voltage VBxe2x80x2 with the predetermined threshold value and then, outputs the output signal VCOM2 having a specific logic value if the value of the detection voltage VBxe2x80x2 is equal to or less than its threshold value. As a result, the charging controller 62 turns the switch 61 off to stop the charging operation toward the second battery pack 50.
As explained above in detail, with the conventional mobile phone shown in FIGS. 1 to 5, the phone body 60 can recognize whether the first or second battery pack 40 or 50 is connected thereto according to the discrimination voltage VA or VAxe2x80x2 generated at the connection point of the resistors 68 and 69, i.e., the discrimination terminal 602. Also, the value of the charging voltage VCHG is adjusted or controlled to be proper for the charging characteristic of the battery pack 40 or 50 recognized.
However, to discriminate between the first and second packs 40 and 50, the discrimination-dedicated terminals 402, 502, and 602 are essentially provided respectively in the first and second packs 40 and 50 and the phone body 60. Thus, there arises a problem that the count of necessary terminals is large and therefore, the mobile phone is unable or difficult to be made more compact and light-weight.
Accordingly, an object of the present invention is to provide a method of detecting the type of a battery pack in a mobile electronic device that detects the type of a battery pack connected in a mobile electronic device even if no dedicated terminals are provided to a battery pack.
Another object of the present invention is to provide a mobile electronic device capable of detecting the type of a battery pack connected even if no dedicated terminals are provided to a battery pack.
Still another object of the present invention is to provide a method of detecting the type of a battery pack in a mobile electronic device that makes the device more compact and more light-weight easily.
A further object of the present invention is to provide a mobile electronic device that can be easily made more compact and more light-weight.
The above objects together with others not specifically mentioned will become clear to those skilled in the art from the following description.
According to a first aspect of the present invention, a method of detecting the type of a battery pack in a mobile electronic device is provided, which comprises the steps of:
(a) providing a first battery pack connectable to a body of a mobile electronic device;
the first battery pack having a battery cell, a first terminal connected to a high-potential side terminal of the cell, a second terminal connected to a low-potential side terminal of the cell, a third terminal, and a temperature detection element connected across the second and third terminals;
(b) providing a second battery pack connectable to the body of the device;
the second battery pack being different in characteristic from the first battery pack;
the second battery pack having a battery cell, a first terminal connected to a high-potential side terminal of the cell, a second terminal connected to a low-potential side terminal of the cell, a third terminal, and a temperature detection element connected across the first and second terminals;
(c) providing the body of the device with a fourth terminal connectable to the first terminal of the first or second battery pack, a fifth terminal connectable to the second terminal of the first or second battery pack, a sixth terminal connectable to the third terminal of the first or second battery pack;
the body of the device having a resistive voltage divider circuit connected among the fourth, fifth, and sixth terminals;
(d) connecting the first or second battery pack to the body of the device in such a way that the fourth, fifth, and sixth terminals of the body of the device are connected to the first, second, and third terminals of the first or second battery pack, respectively;
(e) detecting an output voltage of the resistive voltage divider of the body of the device, generating a detection result; and
(f) judging whether the first or second battery pack is connected to the body of the device base on the detection result.
With the method of detecting the type of a battery pack in a mobile electronic device according to the first aspect of the invention, the first and second battery packs connectable to the body of the mobile electronic device are provided. Each of the first and second packs has the battery cell, the first terminal connected to the high-potential side terminal of the cell, the second terminal connected to the low-potential side terminal of the cell, the third terminal, and the temperature detection element connected across the second and third terminals.
On the other hand, the body of the device is provided with the fourth terminal connectable to the first terminal of the first or second battery pack, the fifth terminal connectable to the second terminal of the first or second battery pack, the sixth terminal connectable to the third terminal of the first or second battery pack. The body of the device further has the resistive voltage divider circuit connected among the fourth, fifth, and sixth terminals.
When the first or second battery pack is connected to the body of the device in such a way that the fourth, fifth, and sixth terminals of the body of the device are connected to the first, second, and third terminals of the first or second battery pack, respectively, the output voltage of the resistive voltage divider is detected, generating the detection result. Thereafter, it is judged whether the first or second battery pack is connected to the body of the device based on the detection result.
Because the temperature detection element is connected across the second and third terminals in the first battery pack while the temperature detection element is connected across the first and second terminals in the second battery pack, the content of the detection result varies according to whether the first or second battery pack is connected to the body of the device.
Accordingly, the fact whether the first or second battery pack is connected to the body of the device can be detected (i.e., recognized). Thus means that the type of the first or second battery pack can be discriminated even if no dedicated terminals are provided to the first and second battery packs. Thus, the mobile electronic device can be made more compact and more light-weight easily.
In a preferred embodiment of the method according to the first aspect of the invention, each of the first and second battery packs comprises a circuit for detecting whether or not the battery cell is in its normal condition; and a switch for stopping an output of the battery cell if the battery cell is not in its normal condition.
In another preferred embodiment of the method according to the first aspect of the invention, the body of the device comprises first, second, and third comparators having threshold values different from each other; and a discrimination circuit for discriminating between the first and second battery packs. The first, second, and third comparators compares the output of the resistive voltage-divider circuit with their threshold values, generating an comparison result signal to the discrimination circuit. The discrimination circuit discriminates between the first and second battery packs based on the comparison result signal.
In this embodiment, it is preferred that the comparison result signal is a combination of three logic signals from the first, second, and third comparators.
According to a second aspect of the present invention, a mobile electronic device is provided, which comprises:
(a) a first battery pack connectable to a body of a mobile electronic device;
the first battery pack having a battery cell, a first terminal connected to a high-potential side terminal of the cell, a second terminal connected to a low-potential side terminal of the cell, a third terminal, and a temperature detection element connected across the second and third terminals;
(b) a second battery pack connectable to the body;
the second battery pack being different in characteristic from the first battery pack;
the second battery pack having a battery cell, a first terminal connected to a high-potential side terminal of the cell, a second terminal connected to a low-potential side terminal of the cell, a third terminal, and a temperature detection element connected across the first and second terminals;
(c) the body of the mobile electronic device having a fourth terminal, a fifth terminal, a sixth terminal, and a resistive voltage divider circuit connected among the fourth, fifth, and sixth terminals;
the first terminal of the first or second battery pack being connectable to the fourth terminal of the body, the second terminal of the first or second battery pack being connectable to the fifth terminal of the body, the third terminal of the first or second battery pack being connectable to the sixth terminal of the body;
(d) an output voltage of the resistive voltage divider of the body being detected to generate a detection result, when the first or second battery pack is connected to the body in such a way that the fourth, fifth, and sixth terminals of the body are connected to the first, second, and third terminals of the first or second battery pack, respectively; and
(e) whether the first or second battery pack is connected to the body is judged based on the detection result.
With the mobile electronic device according to the second aspect of the present invention, because of substantially the same reason as the method according to the first aspect of the invention, the fact that the first or second battery pack is connected to the body of the mobile electronic device can be detected (i.e., recognized) and discriminated without providing dedicated terminals for discriminating between the first and second battery packs.
Also, since no discrimination-dedicated terminals are required, the mobile electronic device according to the second embodiment can be easily made more compact and more light-weight.
In a preferred embodiment of the deice according to the second aspect of the invention, each of the first and second battery packs comprises a circuit for detecting whether or not the battery cell is in its normal condition; and a switch for stopping an output of the battery cell if the battery cell is not in its normal condition.
In another preferred embodiment of the device according to the second aspect of the invention, the body comprises first, second, and third comparators having threshold values different from each other; and a discrimination circuit for discriminating between the first and second battery packs. The first, second, and third comparators compares the output of the resistive voltage-divider circuit with their threshold values, generating an comparison result signal to the discrimination circuit. The discrimination circuit discriminates between the first and second battery packs based on the comparison result signal.
In this embodiment, it is preferred that the comparison result signal is a combination of three logic signals from the first, second, and third comparators.